Remove Public Holidays from Outlook 2010/2013

Click on Calendar
Click on the View tab
Use the drop down button Change View and select List
You should now see a list of all your calendar items
Sort by Category by using the column headings
The holidays should appear grouped together
You can now delete them all by highlighting and pressing Delete

Set Exchange 2010 Online Archive limits

This is not performed on the mailbox database as a global default unfortunately.  This needs to be applied periodically after you set up new mailboxes.

Setting the limit for all mailboxes:

Get-Mailbox | Set-Mailbox –ArchiveQuota 1000MB –ArchiveWarningQuota 500MB